U.S. Pat. Nos. 4,037,688; 4,046,227; 4,046,228; 4,063,620 and 4,111,284, which are all assigned to the same assignee as the present application, disclose a new and improved elevator system in which the strategy utilized by the supervisory control is suitable for implementation by a microprocessor. These patents are hereby incorporated into the present application by reference, and will be hereinafter referred to as the incorporated patents.
The incorporated patents set forth a universal elevator operating strategy which accommodates all possible building configurations in which an elevator car may serve any combination of floors. The car controllers provide complete information to the system processor as to the building configuration which exists at any instant, and thus the supervisory control may be universally applied to any building without any significant modification of the control.
The universal operating strategy periodically assigns the up and down service directions, also called up and down scan slots, respectively, of the floors to the cars by dividing them among all in-service elevator cars within the constraints of predetermined dynamic averages, which distributes the work load evenly among all of the elevator cars. Thus, the car assigned to a specific service direction from a floor will immediately "see" a hall call registered therefrom without any intercession required on the part of the supervisory control system.
Before each new assignment process, the supervisory system control clears all previously assigned scan slots or landing service directions which do not have a registered hall call associated therewith. The supervisory system control then assigns the unassigned scan slots in a plurality of assignment passes, such as three. During the initial assignment pass, each scan slot is examined to see if a car has a car call for the floor associated therewith. If so, a car set for up travel is assigned the up scan slot for this floor if it is not already assigned, and it is not a terminal floor for this car. If it is a terminal floor it would be assigned the down scan slot for this floor. If the car is set for down travel it would be assigned the down scan slot for this floor if it is not already assigned, and it is not a terminal floor for this car. If it is a terminal floor it would be assigned the up scan slot for this car. On the subsequent assignment passes, the scan slots not already assigned are assigned to the cars. The scan slot assignments are made within the restrictions of certain dynamic calculated averages in order to divide the currently existing work load as evenly as possible among all of the in-service elevator cars.
Incorporated U.S. Pat. No. 4,063,620 adds a limit function in the supervisory control which places a limit on automatic car call related assignments. In one embodiment of the limit function, the car call related scan slot assignments are counted. When a predetermined number N of such car call related assignments are made to a car, such as two, or three, as desired, this car will not be assigned any additional scan slots during this assignment process just because they are related to its car calls.
In another embodiment of the limit function, instead of counting the number of car call related scan slot assignments and cutting off such automatic assignments after a predetermined number N have been made, stops to which the car is committed to make due to car and hall calls are counted. These stops are counted and car call related scan slot assignments are made only if the floor associated with the car call is included in the first N stops, such as three stops. Thus, for example if a car has two hall calls assigned to it and the number N is three, only one car call related scan slot assignment will be made to this car if both hall calls are counted before reaching the second car call.